Electric circuit-breaker of the gas-blast type



March 23, 1954 D. F. AMER ELECTRIC CIRCUIT-BREAKER OF THE GAS-BLAST TYPEFiled April 1, 1949 2 Sheets-Sheet l -5 mmnmum E3 E -5 H H y r 2 C c c cE c1 2 41 3 I J2 J p A3 J C2 0. C J2 1 J3 C, 2 J J3 D 1 A2 0 5: 1 I N 2F3 5 F2 F a [44 l 3'6 L i: s

s L M :.;--S Inventor T A ttbrne y March 23, 1954 AMER 2,673,271

ELECTRIC CIRCUIT-BREAKER OF THE GAS-BLAST TYPE Filed April 1, 1949 2Sheets-Sheet 2 rvB Q 9 Inventor A tiorney Patented Mar. 23, 1954ELECTRIC CIRCUIT-BREAKER OF THE GAS-BLAST TYPE Donald Foster Amer,Newcastle-on-Tyne, England, assignor to A. Reyrolle &.Company Limited,Hebburn-on-Tyne, England, a company of Great Britain Application April1, 1949, Serial No. 84,904

Claims priority, application Great Britain April 23, 1948 24 Claims.(01. 200-148) This invention relates to electric circuitbreakers of thegas-blast type in which the contacts separate within an arcing enclosuremaintain'ed'filled with gas under a superatmospheric initial or fillingpressure, a blast of deionising gas flowing from the enclosure to assistin extin'guishing the arc when the circuit-breaker is opened.

If, as in some arrangements, the blast of deionisin'ggas is produced byopening an exhaust valve so'that gas from the enclosure flows through anozzle or vent adjacent to the separating contacts, the initial orfilling pressure within the enclosure necessarily commences to'fall'fromthe initial valuefas soon as the exhaust valve opens. In order,therefore, to were the requisite blast during the separation of thecontacts, a high initial pressure is desirable and the enclosure has tobe mechanically designed to maintain and withstand such pressure. Inconflict with this requirement is the fact that the higher the initialor filling gas pressure the greater the risk of moisture condensationwithin the circuit-breaker.

The invention has for its object to overcome these and otherdifficulties. I

In a circuit-breaker according to the invention, means are providedwhereby the initial or filling gas pressure within the enclosure issupplemented during opening of the circuit-breaker. 7

Theinitial gas pressure may be supplemented by supplying to theenclosurev gas under a pressure exceeding the initial or fillingpressure, or by applying pressure to the gas within the enclosure. 7 a

Preferably, the initial or filling gas pressure does not appreciablyexceed that necessary for the optimum restriking gap between the opencontacts to withstand full voltage, the said initial pressure beingsupplemented during opening of the circuit-breaker to provide therequisite gas blast. V In this way, under normal operating conditions,the contact enclosure only has to withstand and maintain thecomparatively low filling pressure whilst, at the same time, adequategas pressure is available to provide the requisite gas blast without anyfall in pressure at the commencement of the contact separation.Moreover, since the gas pressure within the enclosure does not fallbelow the initial or filling value, the gap between the open contactscan be reduced to a value corresponding to that necessary for effectivearc extinction. V M

The invention may becarried into practice in various ways but fourcon'structions, each embod'yi'ng the invention, are shown diagrammati- 2cally, and by way of example, in Figures 1 to 4 respectively of theaccompanying drawings, the apparatus being shown in longitudinal sectionin each figure. I

In the embodiment shown in Figural, the circuit-breaker comprises ahollow, and externally shedded, post insulator A mounted vertically on,and in open communication with, a metallic base B having incorporated 1therein or I connected thereto a gas supply reservoir B in which a highgas pressure, say 250 pounds per square inch, is maintained. Thereservoir B communicates with the interior of the post insulator Athrough a reducing valve B by which the gas is expanded and supplied ata pressure lower than that within the reservoir B For example this lowergas pressure, hereinafter referredto as the initial or filling pressure,may be of the order of '75 pounds per square inch. The-reservoir Bcommunicates with the interior of the base B through a blast valve Bcontrolled by an opening solenoid S whilst a relief valve B in the baseB is controlled by a closing solenoid S the two solenoids S 8constituting parts of a control circuit S for opening and closing thecircuit-breaker.

Mounted on top of the post insulator A is a cup-like or upwardly flaringmetallic member A constituting the lowerportion of a contact en'-closure C which is completed by a cylindrical and externally sheddedintermediate insulator A disposed on the said lower portion A andcarrying an upper metallic portion or head A The lower metallic portionA? of the enclosure C is provided with an internal spider A whichsupports, in axial alignment with the hollow post insulator A, arod-like fixed contact C which thus extends axially within the enclosureC. The upper wall or head A of the enclosure C has a downwardlyextending metallic skirt D furnished at its lower end with a tubularshroud D of insulating material, the skirt D andshroud D thus extendingdownwards in the annular space between the cylindrical wall of theenclosure C and the fixed contact therein C Formed in the metallic skirtD adjacent to the upper or free end of the fixed contact C is an openingD through which extends a moving contact C operated by a piston Cmovable in a cylinder C extending laterally from the metallic head A ofthe enclosure C, the moving contact C cooperating with a brush contact Celectrically connected to and lying within the said head A The contactpiston C isprovided with a bleed passage C which establishes opencommunication between the enclosure C on one side of the piston C andthe cylinder C on the opposite side thereof, for the purpose describedbelow.

Formed in the upper wall of the metallic head A so as to besubstantially coaxial with the fixed contact C, is a nozzle E flaringupwards into a cooling chamber E whose upper or outlet end has anexhaust port E controlled by an exhaust valve E mounted on a resilientdiaphragm E (e. g. of rubber or springy metal) constituting part of thelower wall of an auxiliary chamber E in open comunication, through ableed pipe E with the interior of the contact enclosure C.

With the circuit-breaker in the closed condition, as shown in Figure 1,the moving contact C extends through the opening D in the metallic skirtD into engagement with the upper end of the fixed contact C the circuitbeing thus completed from the lower metallic portion A of the enclosureconstituting one pole X of the circuit-breaker, and through the fixedand movable contacts C C to the upper portion or head A constituting thesecond pole Y.

Both the blast valve B and the relief valve B in the metallic base B arenow in their closed positions, but the interior of the enclosure C ismaintained filled with gas at an initial or filling pressure of, say,'75 pounds per square inch, from the reservoir B through the reducingvalve 13 The pressure being equalised, through the bleed passage C inthe contact piston C on both sides thereof, the contacts 0 remain in theclosed position. Further the gas pressure is insufficient to open theexhaust valve E and, apart from the gas being comparatively dry due toexpansion by traversing the reducing valve 3, is sufficiently low to bereadily maintained and withstood by the enclosure.

If it is desired to open the circuit-breaker, the opening solenoid S isenergised thus opening the blast valve B so that the reservoir B isbrought into open communication with the interior of the enclosure C.The excess pressure on the inner face of the contact piston C thuscauses the moving contact C to be retracted from the fixed contact Cthereby drawing an arc transversely within the metallic skirt D. Theincreased pressure within the enclosure C is transmitted through thebleed pipe E to the auxiliary chamber E so that the diaphragm E isflexed and the exhaust valve E opened. A blast of deionising gas, at thesupplemented pressure, is thus caused to flow through the nozzle E sothat the end of the arc rooted on the moving contact C is transferredfirst to the adjacent wall of the metallic skirt D and. then to, andthrough, the nozzle E whereby the are is extinguished. After apredetermined interval, the opening solenoid S is deenergised so thatthe blast valve B is closed and the pressure within the enclosure Creturns to the initial or filling pressure, the exhaust valve E at thesame time returning to the closed position due to the fall in pressure.The pressure being again equalised on opposite sides of the contactpiston C the movable contact C remains in its open position.

The initial or filling pressure now obtaining in the enclosure 0, whilstinadequate to provide the requisite gas blast during opening of thecircuitbreaker, is suflicient to withstand full voltage between the opencontacts (3 C across a gap which does not exceed the optimum forefiective extinction by the gas blast produced by the increased pressureduring opening of the circuitbreaker. In this respect it will beapparent that the filling gas pressure at the gap is maintained orincreased except during the closing operation, now to be described.

In order to close the circuit-breaker, the closing solenoid S isenergised so as to open the relief valve 13* in the base B. The suddenpressure drop on the contact side of the contactpiston C allows theinitial-filling-pressure gas at the back of the piston C to cause it tomove inwards thereby moving the movable contact C back through theopening D in the metallic skirt D and into engagement with the fixedcontact C The relief valve B is then reclosed so that the pressurewithin the enclosure C is restored to the initial or filling value.

It will be understood that the invention may be applied either tosingle-break or to multi-break circuit-breakers. Moreover, instead ofthe contacts being movable laterally with respect to the nozzle asdescribed above, the movement of the contacts may be axial with respectto the nozzle or vent. One such construction is shown in Figure 2, inwhich the upper end of the hollow post insulator A carries a shortintermediate cylindrical metallic member F having an internal spider Fwhich supports a pneumatic cylinder F containing a vented piston F atthe lower end of a rod-like movable contact F The contact enclosure G iscompleted by a plurality of short coaxial insulating tubes G mounted inaxial alignment with, and on top of, the cylindrical metallic member F,each insulating tube G being constituted by two annular rings ofinsulating material arranged one within the other and radially spacedapart. The annular spaces C1 between the insulating rings G are in opencommunication with each other and, through a passage G3 in the wall ofthe intermediate cylindrical member F, with the pneumatic cylinder F onthat side of the piston remote from the contact enclosure G.

Thus, for purposes of additional insulation, the supplementary annularspace G in the insulating wall of the built-up contact enclosure Gremains in open communication with the dry-gas space represented by thecontact enclosure G and pneumatic cylinder F the gas trapped in thissupplementary space also assisting the closing movement of the piston Fwhen the pressure within the contact enclosure G is relieved or releasedto reclose the circuit-breaker as described below. The uppermost tube Gis closed by a dome or head plate H having a central internal pin or rodH constituting the fixed contact in axial alignment with the movable contact rod F The short insulating tubes G are axially spaced apart by anumber of metallic rings J each of which has an exhaust pipe J extendingradially from within the enclosure G and through the outer wall thereof.The exhaust pipes J are provided with transverse passages or vents Jlying in alignment with the fixed and movable contacts H, F the outerend of each exhaust pipe J being closed by a spring-loaded exhaust valveJ With the circuit-breaker in its closed condition, the interior of theenclosure G is filled with gas at the initial or filling pressure, thisfilling being maintained from the reservoir B through the reducing valve13 as described above. The movable contact rod F is now in its uppermostposition as shown in Figure 2, that is to say,

so that it extends through all the vents J in the aws em exhaust pipes Jand into engagement with the fixed' contact H, the circuitbeing-established from the cylin'drical metallic member F, constitutingone'pole X of the'circuit-breaker, and through the movable and fixedcontacts-F H to the dome or-head H constituing the second'pole Y.

When-the'circuit-breaker is to Ice-opened, the blastvalve B isopened'byenergising the opening solenoid S so that the initial-or fillingpressure withinthe enclosure G is supplemented and the contact positionF is moved downwards into its "cylinder F As the movable contact F iswithdrawn from thevents J in the lateral exhaust'pipes J the exhaustvalves J are automatically opened by the gas pressure and a blast oftdeionising gas is caused to flow through each vent J After apredetermined interval, the blast valve B3 is closed and the pressurewithin the-enclosure G reverts to the initial or filling valve whereuponthe-exhaust valves -J -close due to the pressure drop.

For closing the circuit-breaker, the relief valve B 1in the base B ofthe circuit-breaker is opened so as to release the pressure within theenclosure G, the'excess pressure on the lower face of the vented contactpiston F then moving the piston and movable contact F upwards intotheclosed position. Having reclosed' the relief valve 13 the pressurewithin the enclosure G automatically returns to the initial or fillingvalue.

For very high voltages it may prove practicable to provide only a closedreception space or expansion chamber for the exhaust gases, the pressurein the said reception space being relieved through a single valve atapredetermined intervalafter the circuit-breaker has been opened. In thearrangement shown in Figure 3, which may either be provided with anautomatically operated exhaust valve as in the construction firstdescribed aboveor with a valve forevacuating the gases from areceptionspace, the axially movable contact rod F carries a piston Fmovable within a cylinder F under the gas pressure within the enclosureG The contact enclosure G comprises two coaxial insulating cylinders G6? disposed one within the other and radially spaced apart, with theannular space G between them in open communication with the pneumaticcylinder F as in the second arrangement described above. In the closedcondition of the circuit-breaker the movable contact rod F extendsthrough or across a plurality of vents or nozzles K constituting themouths of expansion chambers K K K disposed within the enclosure G Whenthe circuit-breaker is opened by supplementing the gas pressure withinthe enclosure G the movable contact F is withdrawn from, so as to open,the vents or nozzles K and blasts of gas flow therethrough to assist inextinguishing the arc.

In the construction shown in Figure 4-, the re ception or expansionchamber and the enclosure together constitute a self-contained andenclosed gas circuit. The movable contact L moves relatively to thefixed contact rod M in a direction transverse to the axis of theassociated nozzle N, as in the construction first described above, thecylinder L of the contact piston L on that side thereof remote from theenclosure, being in open communication through a bleed passage L with areception chamber N on the low pressure side of the nozzle N. Thecontact enclosure 0 on the high pressure side of the nozzle N is in opencommunication with a reservoir P formed in the base of thecircuit-breaker, and pressure control pistons Q are movable in acylinder Q whose upper and lower ends are respectivelyin opencommunicationswith the reception chamber N on the low pressure side ofthe nozzle N and the contact enclosure 0 on thehigh-pressure'side of thenozzle N. The rod-Q of the pressure-control pistons Q carries'at itslower end an actuating piston P movable in a cylinder P disposed withinthereservoir P and having 'anassociated closing valve P and. openingvalve P When the circuit-breaker is in the closed condition, thepressure-control pistons Q are in their uppermost positions and the gaspressure, throughoutthe gas circuit, including the reservoir P, contactenclosure 0 and reception chamber N1, is at the initial or fillingvalue, 1. e.the pressure within the reservoir P. To-openthecircuitbreaker, the opening valve P is operated'so that thepressure-control pistons Q move downwards and thus apply pressure to thegas in the enclosure 0 whilst at the same time reducing the pressure inthe reception chamber N The increased pressure in the contactenclosureoassisted bythe reduced pressure in the reception chamber Nmoves the contact piston L and therefore the moving contact L, outwardsaway from the fixed contact M. The increased gas pressure on the highpressure side of the nozzle N accompaniedby the simultaneous reductionin pressure on the low pressure side of the nozzle provides thenecessary gas blast through the nozzle N for extinguishing the arc.

For closing the circuit-breaker, the closing valveP is operated so thatthe pressure-control pistons Q move upwards, thereby decreasing thepressure within the enclosure 0 so that the movable contaot piston Lassisted now by the increased pressure in'the reception chamber N movesinto engagement with the fixed contact rod M. The pressure thenequalises throughout the system at the initial or filling value.

B suitably proportioning the gas spaces on the high and low pressuresides of the nozzle N respectively, a normally maintained initial orfilling gas pressure of, say, four atmospheres can be converted, byoperation of the pressure control piston Q, to a pressure of eightatmospheres on the high pressure side of the nozzle N and a pressure ofone atmosphere on the low pressure side, thereby producing an adequategas blast through the nozzle N during opening of the circuit-breaker.

When the exhaust valve is live, as in known superatmospheric-filledopen-type circuit-breakers, the valve has to be operated by some form ofnon-conducting mechanical coupling or independent pneumatic means. Theinvention, however, permits operation of the exhaust valve Without suchindependent operating means. Further, since the gap between the opencontacts lies in an atmosphere of gas at a pressure not less than thesuperatmosph'eric filling pressure throughout the opening movement andwhile the circuit-breaker remains open, the said gap can be reduced to avalue which, while short enough to satisfy requirements of arcextinction, is yet sufiiciently long to meet requirements of isolationwithout the provision of additional seriesbreak isolating means, since,for usual gap "configuration, the curve of dielectric break-downstrength plotted against air-pressure rises steep- 1y at its origin. Inthe latter respect, the initial or filling gas pressure maintained inthe contact enclosure while the contacts are open need not exceed thatnecessary to ensure that a normal gap will withstand full voltage. Forexample.

the initial pressure may be about one third of that to which the gaspressure is raised during arc quenching.

What I claim as my invention and desire to secure by Letters Patent is:

1. A gas-blast electric circuit-breaker comprising an arcing enclosure,a restricted nozzle leading from such enclosure, two relatively movablecooperating contacts adjacent to the nozzle within the enclosure, meanswhereby the enclosure is maintained filled with gas under asuperatmospheric initial or filling pressure, means whereby ablast ofdeionising gas is caused to flow from the enclosure past the contactsand through the nozzle in timed relation with the separating movementthereof so as to assist in extinguishing the are drawn between theseparating contacts, and means whereby the pressure within the enclosureis reinforced during the flow of the said blast thereby preventingreduction of the pressure within the enclosure below the said initial orfilling value.

2. A gas-blast electric circuit-breaker comprising an arcing enclosure,a restricted nozzle leading from such enclosure, means whereby theenclosure is maintained filled with gas at a superatmospheric initial.or filling pressure, two coopcrating contacts adjacent to the nozzlewithin the enclosure, at least one of said contacts being movable, acylinder, a piston within the cylinder and operatively connected to themovable contact, said piston being exposed to the gas pressure withinthe enclosure, and means whereby the gas pressure within the enclosureis supplemented so as to move said piston and separate the contactswhilst at the same time causing a blast of deionising gas to flow fromtheenclosure past the separating contacts and through the nozzle toassist in extinguishing the are drawn between them, the saidsupplementation of the pressure preventing reduction of the pressurewithin the enclosure below the initial or filling value during the flowof the said blast.

3. A gas-blast electric circuit-breaker comprising an arcing enclosurehaving a restricted discharge nozzle or vent, two cooperating contactswithin the enclosure on the high pressure side of the vent, at least oneof said contacts being movable, an exhaust valve opening to atmosphereon the low pressure side of the vent, means whereby the enclosure ismaintained filled with gas at a superatmospheric initial or fillingpressure, means whereby the exhaust valve is opened to cause a blast ofdeionising gas to fiow from the enclosure and past the contacts throughthe nozzle, and means whereby the gas pressure within the enclosure isreinforced during the flow of the blast thereby preventing reduction ofthe pressure within the enclosure to a value less than the initial orfilling pressure.

4. A gas-blast electric circuit-breaker comprising an arcing enclosure,an exhaust valve controlling the discharge of gas from the enclosure,two relatively movable cooperating contacts within the enclosure, meanswhereby the exhaust valve and the contacts are opened in timed relation,means whereby gas under pressure is supplied to the enclosure so as tomaintain the enclosure filled with gas under a superatmospheric initialor filling pressure while the exhaust valve is in the closed position,and means whereby the supply of gas under pressure to the enclosure issupplemented when the exhaust valve is opened, so that, though openingof the exhaust valve causes a blast of deionising gas to flow from theenclosure and past the separating contacts to assist in extinguishingthe are drawn between them, reduction of the gas pressure within theenclosure below the initial or filling value is prevented by thesupplementary gas supply.

5. A gas-blast electric circuit-breaker comprising an arcing enclosure,an exhaust valve controlling the discharge of gas from the enclosure,two relatively movable cooperating contacts within the enclosure, meanswhereby gas under pressure is supplied to the enclosure so as tomaintain the enclosure filled with gas under a superatmospheric initialor filling pressure while the exhaust valve is in the closed position,means whereby the exhaust valve and the contacts are opened in timedrelation by a gas pressure within the enclosure above the said initialor filling value, and means whereby the supply of gas to the en--closure is supplemented to open the exhaust valve and the contacts sothat, though opening of the exhaust valve causes a blast of deionisinggas to fiow from the enclosure and past the separating contacts so as toassist in extinguishing the are drawn between them, reduction of the gaspressure within the enclosure below the initial or filling value isprevented by the supplementary gas supply.

6. A gas-blast electric circuit-breaker comprising an arcing enclosure,an exhaust valve controlling the discharge of gas from the enclosure,two relatively movable cooperating contacts within the enclosure, meanswhereby gas under pressure is supplied to the enclosure so as tomaintain the enclosure filled with gas under a superatmospheric initialor filling pressure while the exhaust valve is in the closed position,means whereby the exhaust valve and the contacts are opened in timedrelation by a gas pressure within enclosure above the said initial orfilling value, means whereby the supply of gas to the enclosure issupplemented to open the contacts and exhaust valve, so that thoughopening of the exhaust valve causes a blast of deionising gas to fiowfrom the enclosure and past the separating contacts so as to assist inextinguishing the are drawn between them, reduction of the gas pressurewithin the enclosure below the initial or filling value is prevented bythe supplementary gas supply, and a relief valve which, when opened,releases the pressure within the enclosure thus closing the exhaustvalve and the contacts.

'7. A gas-blast electric circuit-breaker compris ing an arcing enclosurehaving a restricted discharge nozzle or vent, an exhaust valve on thelow pressure side of the vent and controlling the discharge of gas fromthe enclosure through the vent, a valve-control chamber the pressure inwhich operates the exhaust valve, a bleed conduit interconnecting saidchamber and the enclosure on the high pressure side of the vent, twocooperating contacts within the enclosure, at least one of said contactsbeing movable, a cylinder in open communication with the enclosure, avented piston movable within the cylinder and operatively connected tothe movable contact, means whereby gas under pressure is supplied to theenclosure so as to maintain the enclosure filled with gas under asuperatmospheric initial or filling pressure while the exhaust valve isin the closed position, the gas pressure within the enclosure necessaryto operate the exhaust valve and piston exceeding the said when thecircuit-breaker is to be opened, the

aevaan supply of gas under pressureto the enclosure-is supplemented toraise the pressure therein to' a value exceeding the initial or fillingpressure thereby opening the exhaust valve and operatingthepistontoseparate the contacts, so that though opening of the exhaust valvecauses a blastof deionising gas to flow from the enclosure past theseparating contacts andthrough the vent so as to assist inextinguishing-thearc drawnbetween the contacts, reduction of the gaspressure within the enclosure below the initial or fill ing valueisprevented by thesupplementarygas supply:

8; Agas-blast electric circuit-breaker comprising an arcing enclosurehaving a restricted di"- charge nozzle or vent, an exhaust valve on-thelow pressure side of the vent and controlling the discharge of gas fromthe enclosure through-the vent, a valve-control'chamberthepressure-in'which operates the exhaustvalve, a bleed condui-t-interconnecting' saidchamber and-the enclosure on the high pressure side of the vent; two

cooperating contacts within the enclosure, at least one ofsaid'contacts-being movable a cylinder in open communication with theenclosure, a piston movable within the cylinder and operativelyconnected to the movable contact, means whereby gas under pressure issupplied to the enclosure so as to maintain the enclosure filled withgas'undera superatmospheric initial or filling pressure while theexhaust valve is in the closed position, thegas pressure within the en'-closure; necessaryto operate the exhaust valve and piston exceeding theinitial or filling pressure, means whereby, when thecircuit-breaker is.

to-be opened, theisupplyyof gas under pressure within the enclosureissupplemented to raise the pressure therein to a value exceeding theinitial.

or filling pressure thereby opening, the exhaust valve andoperating thepiston. to separate the contacts, so that though openingof the exhaustvalve causes a blast of deionising gas to flow from.

the enclosure past the separating contacts and through the vent. so asto assist in extinguishing the are drawn between thecontacts,'reducti'on of the gas pressure within the enclosure below theinitial or fillingvalueis prevented by the supplementary gas supply, anda relief valve which, when opened, releases the pressure within theenclosure thus causing the exhaust valve and movable contact to reclose.

9.3 A gas-blast electric circuit-breaker comprising an arcing enclosure,an exhaust valve controllingthe dischargeof gas from the enclosure, two;relatively movable cooperating contacts within the enclosure, meanswhereby the exhaust valve and contacts are opened in timed relation, areservoir containing gasvunder superatmospheric pressure, a primary gassupplycon-v duit connecting the reservoir to the enclosure, a,

reducingvalve determining, the supply of gas through the primary conduitto the enclosure which is thus maintained filled with gas at asuperatmospheric initial or filling, pressure, as determined bythereducing valve, while the exhaust valve ,is, in the closed position, asupple mentary gas suppl conduit connecting the reservoir to theenclosure, anda blast valve control lingsa-id supplementary conduit, theblast valve being opened when the exhaust valve is opened so that,though opening of the exhaust valve causes a blast of deionising gas tofiow'from the enclosure and past the separating contacts to assist inextinguishing the arc -drawn'between them, reduction of the gas pressurewithin the 10.3 enclosure below the initial or filling value ispreventedby the supplementary gas supply.

10. A gas-blast electric circuit-breaker as claimed in claims, in whichthe exhaust valve and the contacts are opened by a gas pressureprising'an arcing' enclosure having a restricted:

discharge nozzle or: vent; an exhaust valveon the lowpressure side ofthevent and controlling.

the discharge of gas from the enclosure through the-vent, avalve-control chamber the pressure in which operates the exhaust valve ableed conduit interconnecting said chamber and theenclosure on the highpressure side of the vent;

two cooperating contacts within the enclosure,

at least one of said contacts being movable, a

cylinder in open communication with-the enclosure on the high pressureside of the vent, .a:

vented piston movablewithin said cylinder and operatively connected to 1the movable contact, a reservoir containing gas under superatmosphericpressure, a primary gas supply conduitconnecting the reservoir to theenclosure, a reducing valve determining the supply of gas through theprimary conduit to the enclosure which is thus maintained filled withgas atasuperatmospheric initial or fillingpressure, as

determined by=the-reducing valve, while the ex haust valve is in theclosed position, a supplementary gas supply conduit connecting thereservoir to the enclosure, a blast valve controlling the supply ofgas-through the supplementary conduit, and a relief valve which, whenopened; relieves the pressure within the enclosure and thus "causes theexhaustvalve and contacts to reclose, so'that when the circuit-breakeris to be opened, the blast valve is openedwhereby'the exhaust valve andthe movable contact are moved into their open positions and, though ablast of deionising gas is thus caused to fiow from the enclosure andpast the separating contacts to the vent, thus assisting inextinguishing the arc drawn between the contacts, reduction of'the'pressure within the enclosure to a value below the initial or fillingpressure is prevented by the supplementary gas supply,and when thecircuitbreaker is to be closed, the'relief valve is opened" so that theexhaust valve and the movable contact are'restored-to theirclosed'positions;

13. A gas-blast electric circuit-breakercomprising an arcing enclosurehaving at least one discharge nozzle or vent, a gas-expansion cham bercommunicating with said vent, two cooperating contacts within theenclosure, at least one of said contacts being movable and, when in itsclosed position, extending into, so as to close,

the vent, a cylinder, a vented'piston operatively" connected to themovable contact and slidable within said cylinder-which is in opencommunication with the enclosure through the vent in the piston, meanswherebygas underpressure is supplied to the enclosure so that theenclosure is maintained filled with gas at a superatmospheric initial orfilling pressure, and means whereby the supply of gas under pressure tothe enclosure can be supplemented, thereby operating the piston andwithdrawing the movable contact from the vent so that, though a blast ofdeionising gas is thus caused to flow through the vent and past theseparating contacts to the expansion chamber, thus assisting inextinguishing the are drawn between them, reduction of the pressurewithin the enclosure below the initial or filling value is prevented bythe supplementary gas supply.

14. A gas-blast circuit-breaker as claimed in claim 13, in which thedischarge of gas from the gas-expansion chamber is controlled by aspringloaded exhaust valve.

15. A gas-blast electric circuit-breaker as claimed in claim 13, havinga relief valve which, when opened, relieves the pressure within theenclosure so that the pressure within the cylinder predominates andrestores the movable contact to its closed position.

16. A gas-blast electric circuit-breaker comprising an arcing enclosurehaving at least one discharge nozzle or vent, a gas-expansion chamber,communicating with said vent, two cooperating contacts within theenclosure, at least one of said contacts being movable and, when in itsclosed position, extending into, so as to close, the vent, a cylinder, avented piston operatively connected to the movable contact and slidablewithin said cylinder which is in open communication with the enclosurethrough the vent in the piston, a reservoir filled with gas under superatmospheric pressure, a primary gas-supply conduit connecting thereservoir to the enclosure, a reducing valve determining the supply ofgas through the primary conduit to the enclosure, so

that the enclosure is maintained filled with gas at a superatmosphericinitial or filling pressure, a supplementary gas supply conduitconnecting the reservoir to the enclosure, and a blast valve controllingthe supply of gas under pressure through the supplementary conduit tothe enclosure, opening of the blast valve causing the gas pressurewithin the enclosure to be supplemented whereby the piston is operatedto withdraw the movable contact from the vent so that, though a blast ofdeionising gas is thus caused to flow from the enclosure, past theseparating contacts and through the vent to the expansion chamber,thereby assisting in extinguishing the are drawn between the contacts,reduction of the pressure within the enclosure to a value below theinitial or filling pressure is prevented by the supplementary gassupply.

1'7. A gas-blast circuit-breaker as claimed in claim 16, having a reliefvalve which, when opened, relieves the pressure within the enclosure sothat the pressure within the cylinder predominates and restores themovable contact to its closed position.

18. A gas-blast electric circuit-breaker comprising an arcing enclosurehaving at least one discharge nozzle or vent, a gas-expansion chambercommunicating with said vent, two cooperating contacts within theenclosure, at least one of said contacts being movable and, when in itsclosed position, extending into, so as to close, the vent, a cylinder, avented piston operatively connected to the movable contact and slidablewithin said cylinder which is in open communication with the enclosurethrough the vent in the piston, an exhaust valve controlling thedischarge of gas from the enclosure, a valvecontrol chamber the pressurein which operates the exhaust valve, a bleed conduit communicatingbetween the enclosure and said valve-control chamber, means whereby gasunder pressure is supplied to the enclosure so that the enclosure ismaintained filled with gas at a superatmospheric initial or fillingpressure, and means whereby the supply of gas under pressure to theenclosure can be supplemented, thereby operating the piston to withdrawthe movable contact from the vent so that, though a blast of deionisinggas is thus caused to flow through the vent and past the cooperatingcontacts to the expansion chamber and past the exhaust valve, thusassisting in' extinguishing the are drawn between the contacts,reduction of the pressure within the enclosure below the initial orfilling value is prevented by the supplementary gas supply.

19. A gas-blast electric circuit-breaker as claimed in claim 18, havinga relief valve which, when opened, relieves the pressure within theenclosure so that the pressure within the cylinder predominates andrestores the movable contact to its closed position.

20. A gas-blast electric circuit-breaker comprising an arcing enclosurehaving at least one discharge nozzle or vent, a gas expansion chambercommunicating with said vent, two cooperating contacts within theenclosure, at least one of said contacts being movable and, when in itsclosed position, extending into, so as to close, the vent, a cylinder, avented piston operatively connected to the movable contact and slidablewithin said cylinder, an exhaust valve controlling the discharge of gasfrom the enclosure and expansion chamber, a valve-control chamber thepressure in which operates the exhaust valve, a bleed passagecommunicating between the said chamber and the enclosure, a reservoirfilled with gas under superatmospheric pressure, a primary gas-supplyconduit connecting the reservoir to the enclosure, a reducing valvedetermining the supply of gas through the primary conduit to theenclosure, so that the enclosure is maintained filled with gas at asuperatmospheric initial or filling pressure, a supplementary gassupplyconduit connecting the reservoir to the enclosure, and a blast valvecontrolling the supply of gas under pressure through the supplementaryconduit to the enclosure, opening of the blast valve causing the gaspressure within the enclosure to be supplemented whereby the piston isoperated to withdraw the movable contact from the vent so that, though ablast of deionising gas is caused to flow from the enclosure, past theseparating contacts and past the exhaust valve from the vent andexpansion chamber, thereby assisting in extinguishing the are drawnbetween the contacts, reduction of the pressure within the enclosure toa value below the initial or filling pressure is prevented by thesupplementary gas pp y.

21. A gas-blast electric circuit-breaker as claimed in claim 20, havinga relief valve which, when opened, relieves the pressure within theenclosure so that the pressure within the cylinder predominates torestore the movable contact to its closed position, the predominatingatmospheric pressure at the same time predominating over that in thevalve-control chamber to restore the exhaust valve to its closedposition.

22. A gas-blast electric circuit-breaker comprising an arcing enclosurehaving a discharge vent or nozzle, an expansion chamber communi eatingwith the low pressure side of the nozzle, a pressure chambercommunicating with the enclosure on the high pressure side of thenozzle, two cooperating contacts within the enclosure on the highpressure side of the nozzle, at least one of said contacts being movableunder the gas pressure within the enclosure, a cylinder communicating atopposite ends respectively with the expansion chamber and. pressurechamber, a piston slidable within said cylinder, means whereby theenclosure is maintained filled with gas under a superatmospheric initialor filling pressure, means whereby the piston is operated in onedirection to supplement the pressure in the enclosure and reduce thepressure in the expansion chamber thus moving the movable contacttowards the open position and causing a blast of deionising gas to flowfrom the enclosure and past the separating contacts to the nozzle,thereby assisting in extinguishing the are drawn between the contactswhilst preventing reduction of the gas pressure within the enclosurebelow the initial or filling pressure, and means whereby the piston isoperated in the reverse direction to reduce the pressure in theenclosure thereby restoring the movable contact to the closed position.

23. A gas-blast circuit-breaker as claimed in claim 22, in which theenclosure and the cylinder are in permanent open communication with areservoir containing gas under the initial or filling gas pressure.

24. A gas-blast circuit-breaker as claimed in claim 22, in which themovable contact is operatively connected to a piston movable in acylinder one end of which is in open communication with the arcingenclosure on the high pressure side of the nozzle whilst the other endof the cylinder is in open communication with the expansion chamber onthe low pressure side of the nozzle.

DONALD FOSTER AMER.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,375,983 Thomson Apr. 26, 1921 1,937,482 Ruppel Nov. 28, 19332,280,321 Thommen Apr. 21, 1942 2,367,934 Flurscheim Jan. 23, 19452,382,274 Trencham Aug. 14, 1945 2,392,647 Cox Jan. 8, 1946 2,459,600Strom Jan. 18, 1949 2,500,429 Nijland Mar. 14, 1950 2,531,617 Forwald.Nov. 28, 1950

